361e32eeaa
Since the standard range adaptors are specified to derive from the empty class view_base, having their first data member store the underlying view is suboptimal, for if the underlying view also derives from view_base then the two view_base subobjects will be adjacent; this prevents the compiler from applying the empty base optimization to elide away the storage for these two empty bases. This patch improves the situation by declaring the _M_base data member last instead of first in each range adaptor that has more than one data member, so that the empty base optimization can apply in more cases. libstdc++-v3/ChangeLog: * include/std/ranges (filter_view): Declare the data member _M_base last instead of first, and adjust constructors' member initializer lists accordingly. (transform_view): Likewise. (take_view): Likewise. (take_while_view): Likewise. (drop_view): Likewise. (drop_while_view): Likewise. (join_view): Likewise. (split_view): Likewise (and tweak nearby formatting). (reverse_view): Likewise. * testsuite/std/ranges/adaptors/sizeof.cc: Update expected sizes. |
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